JP2659570B2 - Electronic still camera and strobe for electronic still camera - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an electronic still camera and a strobe for an electronic still camera.

(Background of the Invention) A normal electronic still camera performs exposure and accumulation for a predetermined time in a light receiving unit of a solid-state imaging device, and then ends the exposure by transferring charges to a transfer unit. The strobe emits light only once during this exposure period.

Normal strobes include those that use the entire charge of the capacitor for light emission, and those that stop light emission when the reflected light from the subject reaches an appropriate level.

(Problems to be Solved by the Invention) When flash photography is performed, a subject close to the camera or a subject with high reflectance tends to be white.

You can also adjust the aperture according to those subjects,
If the emission of the auto strobe is stopped halfway, there is a problem that a subject that is a little distant or a subject with low reflectance is blackened.

In such a case, it is inevitable for a distant subject to which the strobe light does not reach at all, but it is troublesome if the subject is close to the camera and is slightly blacked out.

Such a problem has also occurred when shooting with a normal light source. As a means to solve this, 1978 National Conference on Television Affairs, p. 43-44 [Kne of CCD image sensor
e-characteristic control], and Japanese Patent Application No. 62-87393 filed by the present applicant. However, these methods all perform exposure in a plurality of times, so that there is a problem that it is not possible to cope with stroboscopic photography in which a trigger signal emits light only once.

The present invention has been made in view of the above-described problems, and an object of the present invention is to provide an electronic still camera in which an obtained image is not distorted in white or black even if there is a difference in reflectance or distance. Another object of the present invention is to realize a strobe for an electronic still camera.

(Means for Solving the Problems) The invention according to claim 1 for solving the above problems is an electronic still camera used with a strobe that emits light in synchronization with an external timing signal and provided with a solid-state imaging device. A timing signal supply means for supplying a plurality of timing signals to the strobe during one frame of photographing time, and an electronic shutter operation of the solid-state imaging device during at least one of the flashes. And a light-receiving-amount adjusting means for adjusting the amount of received light.

According to a second aspect of the present invention, there is provided an electronic still camera which is used together with a strobe whose start and stop of light emission are controlled by an external light emission start signal and a light emission stop signal, and which captures a still image. A flash start signal and a flash stop signal applying means for applying a plurality of sets of a flash start signal and a flash stop signal to the flash during flash shooting, and a plurality of flash start signals and a flash stop signal; At least one of the sets includes a time interval control unit that makes the time interval from the light emission start signal to the light emission stop signal different from the time intervals of the other sets.

According to a third aspect of the present invention, there is provided a strobe for use with an electronic still camera having a solid-state imaging device, wherein a plurality of sets are provided from the electronic still camera within one frame of photographing time during strobe photographing. At least one set is a light emission start signal and a light emission stop signal, wherein at least one set is based on a signal in which a time interval between the light emission start signal and the light emission stop signal is different from those of the other sets. Means are provided.

The invention according to claim 4 which solves the above problem emits light a plurality of times within a shooting time of one frame, and is used together with a strobe in which at least one of the plurality of light emissions is different from the other light emission amounts. An electronic still camera according to claim 1, further comprising light emission start signal generating means for generating a light emission start signal for causing said strobe to emit light a plurality of times.

According to a fifth aspect of the present invention, there is provided a strobe for use with an electronic still camera, wherein the strobe emits light a plurality of times within a shooting time of one frame in synchronization with a light emission timing signal from the electronic still camera. At least one of the plurality of times of light emission is provided with a light emitting means that emits light with a different light emission amount from other times.

(Operation) In the electronic still camera according to the first aspect of the present invention, at the time of flash shooting, the flash is emitted a plurality of times within one frame shooting time, and the electronic shutter operation of the solid-state imaging device is performed during at least one of the flashes. By doing so, the amount of received light is adjusted.

In the electronic still camera according to the second aspect, a plurality of strobe light emission start signals and a plurality of light emission stop signals are generated within one frame of shooting time during strobe shooting, and at least one of time intervals from the light emission start signal to the light emission stop signal. 1
The times are different from other time intervals.

In the electronic still camera strobe according to the third aspect, the start and stop of the strobe light emission are controlled by a plurality of sets of light emission start signals and light emission stop signals provided from the electronic still camera.

The electronic still camera according to the fourth aspect generates a light emission start signal so that the strobe emits light a plurality of times.

The electronic still camera strobe according to claim 5, emits light a plurality of times within one frame shooting time in synchronization with a light emission timing signal from the electronic still camera, and emits at least one of the plurality of times of light. Differs from other light emission amounts.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a configuration diagram showing the overall configuration of an embodiment of an electronic still camera according to the present invention. In FIG. 1, reference numeral 1 denotes a solid-state imaging device (hereinafter, referred to as CCD) for converting a light image formed by a lens system 11 described later into an electric signal (image data); Lens system for connecting the CCD1 to the CCD1, 12 is an amplifier for amplifying the output of the CCD1, 13 is a process circuit for converting the output of the CCD1 to a video signal, and 14 is for recording the video signal on the video floppy 15. The recording circuit that converts the signal into
A photometric circuit that calculates the photometric value for performing exposure control from the output of CCD1, and 17 is a CP that controls the whole unit in addition to the exposure control
U and 18 are CCD driving circuits for driving the CCD1. this
It is assumed that the CCD drive circuit 18 has an electronic shutter function for adjusting the shutter speed by adjusting the charge readout timing.

FIG. 2 is a time chart showing a driving pulse when driving the CCD1. Note that the CC that generates this drive pulse
The D drive circuit can be realized by slightly modifying a known circuit, and a detailed circuit configuration is omitted.

FIG. 3 is a configuration diagram showing a configuration of a main part of the CCD 1 used in the above-described embodiment. Here, interline CC as CCD1
The case of D will be described. In the figure, reference numeral 2 denotes a light receiving unit for generating electric charge according to the amount of received light, 3 denotes a vertical transfer unit for vertically transferring the electric charge generated in the light receiving unit, and 4 denotes a horizontal transfer unit for transferring the electric charge from the vertical transfer unit in the horizontal direction. It is a transfer unit. Here, 3 × 4 pixels are shown.

Further, it is assumed that the potentials of the light receiving section 2 and the vertical transfer section 3 of the CCD 1 are as shown in FIG. 4 or FIG. In other words, it is assumed that the transfer unit can store five times the charge of the light receiving unit.

Hereinafter, the operation of the embodiment of the present invention will be described with reference to FIGS.

Assuming that A in FIG. 2 is the exposure period and B is the readout period, the charges of the pixels corresponding to φV1 to φV4 are transferred to the vertical transfer unit 3 first, and then the charges are discarded by reverse transfer. Thereafter, charge transfer from the light receiving unit 2 to the vertical transfer unit 3 is performed in five times (T1, T2, T3, T4, and T5), and the sum added on the vertical transfer unit 3 is read in the period B. In each of the five divided exposure periods, a strobe light is emitted (FIG. 2 (d)).
(G)). The characteristics can be changed by changing the intensity of the strobe light emission (FIGS. 2 (e) to (g)).

As shown in (d), when the light emission amounts of the five times are set to be equal, it is the same as the case where the normal reading is performed by the conventional strobe light emission (FIG. 2 (h)).

When only the fifth light emission amount is reduced as in strobe light emission 2 (FIG. 2 (e)), the reflectance of the subject and the CC
The relationship between the output charges of D1 is as shown in FIG. here,
The case where the fifth light emission amount is 1/4 of the first to fourth light emission amounts will be described. The charge generated by the first to fourth flash emission is as shown in FIG. 6A, and the charge generated by the fifth flash emission is as shown in FIG. 6B. Therefore, when the charges for five times are added, the characteristic shown in FIG. 6C is obtained. That is, a knee characteristic appears due to the difference between the characteristics of A and B. Therefore, even a subject having a high reflectance does not saturate.

When the ratio of the light emission amounts is 16: 16: 4: 4: 1 as in the case of strobe light emission 3 (FIG. 2 (f)), the relationship between the reflectance of the subject and the output charge of the CCD 1 is 7 As shown in FIG. The charge generated by the first and second flash emission is shown in Fig. 7A.
The charge generated by the third and fourth strobe light emission is as shown in FIG. 7B, and the charge generated by the fifth strobe light emission is as shown in FIG. 7C. Therefore, when the charges for five times are added, the characteristic shown in FIG. 7D is obtained. That is, A, B,
The knee characteristic appears due to the difference in the characteristic of C. For this reason,
The output does not saturate even for a subject having a high reflectance.

When the ratio of the light emission amounts is 16: 4: 4: 4: 1 as in the case of strobe light emission 4 (FIG. 2 (g)), the relationship between the reflectance of the subject and the output charge of the CCD 1 is 7 As shown in FIG. The charge generated by the first flash emission is as shown in FIG. 7A, the charge generated by the second, third, and fourth flash emission is as shown in FIG. 7B, and the charge generated by the fifth flash emission is 7 As shown in FIG. Therefore, when the charges for five times are added, the characteristic shown in FIG. 7E is obtained. That is, A,
A knee characteristic appears due to the difference between the characteristics of B and C. Therefore, the output does not saturate even for a subject having a high reflectance.

As described above, by changing the amount of light emitted from the strobe, various other characteristics can be obtained.

FIG. 8 is a circuit diagram showing, for reference, a circuit configuration of a normal strobe. The operation of this strobe is as follows. When turning on the main switch SW _M, the power supply voltage E by the boost circuit 10a is charged is boosted to the capacitor C _1. When the voltage charged in the capacitor C ₁ reaches a predetermined value, neon tube Ne emits light, notifying the completion of charging. At this time, when SW _X is turned on by the X contact signal from the camera,
A spike-like voltage is applied to the discharge tube Xe by the discharge current of the capacitor Cs. The spike voltage becomes a trigger of starting the discharge, charges the capacitor C ₁ is a discharge tube flow, the discharge (light emission) is performed. When the charging electric charge of the capacitor C ₁ is eliminated, the discharge is terminated.

FIG. 9 is a circuit diagram showing a circuit configuration of the strobe light of the present invention. In this configuration, the charging capacitor _{C 1, C 2, C 3} ,
Five switches C ₄ and C ₅ are provided, and the switch SW _C is switched by an instruction from the controller 10b. Therefore, by adjusting the capacitance of each capacitor, FIG.
Light emission characteristics as shown in (g) can be easily realized.

FIG. 10 is a circuit diagram showing an example of the configuration of the controller 10b and the switch SW _C. Fig. 11 shows the controller
It is a time chart at the time of operation of 10b. One shot multi MM1 receives X contact signal from electronic still camera,
Generates a pulse longer than the flash emission time (about 1 ms). Then, the one-shot multi MM2 receives this pulse and generates a pulse synchronized with the fall of the output pulse of MM1. The 2-bit counter receives the output pulse of MM2 and generates C ₀ , C ₁ , and carry. Then, pulses D ₀ , D ₁ , D ₂ , D ₃ , and D ₄ having different phases are output from the 2to4 decoder and the inverter INV. These pulses D ₀ ,
D _1, the D _2, D _3, D ₄ switch SW _C is turned on / off control. For Figure 11, when the pulse _{D 0, D 1, D 2} , D 3, D 4 is low, the contacts of the switch SW _C is turned on. In this manner, the plurality of capacitors of the strobe are switched by the X contact signal from the electronic switch camera, and light emission is performed a plurality of times. FIG. 12 is a circuit diagram showing another example of the circuit configuration of the strobe of the present invention. is there. In this configuration, the controller 10b controls the start and stop of light emission so that a single capacitor performs light emission control a plurality of times. That is, to start light emission is on the switch SW _X, the luminescence by turning off the switch SW _K is stopped by adjusting the light emission amount in the light-emitting. Thus, by controlling the timing of turning off the switch SW _K, it can be adjusted for each light emission amount. FIG. 13 is a time chart when such control is performed. In this example, 5
Only the amount of light emission at the second time is small.

FIG. 14 is a circuit diagram showing a configuration example of a controller of the strobe light shown in FIG. Here, except when the carry of the 2-bit counter is output, the one-shot multi-MM
The strobe emits light for the duration of two longer pulses. Light emission is stopped at the fall of the output pulse of the one-shot multi MM4. When the carry is present, light emission is performed during the shorter pulse of the one-shot multi MM1, and light emission stops at the fall of the output pulse of the one-shot multi MM4. Further, since the start of light emission is always performed at the rise of the one-shot multi MM3, it is necessary that the pulse width be longer than the full light emission time of the strobe.

Note that it is also possible to directly control the strobe from the electronic still camera side without disposing a controller on the strobe side. Therefore, the strobe 10 shown in FIG.
Except for b, it is to control the switch SW _X and SW _K the signal shown in Figure 15. In this case, both switches should be turned on when the signal in FIG. 15 is at a low level.

A method is also conceivable in which the light emission amount of the strobe is set to be the same each time, and the light reception amount is adjusted on the electronic still camera side. For this purpose, the aperture may be adjusted, but when high speed is required, the electronic shutter operation of the CCD is appropriate. FIG. 16 shows an example of such an electronic shutter operation. Here, the charge is read out from the light receiving section of the CCD during the fifth time of the strobe light emission (FIG. 16 (e)). Therefore, the light emission after the charge readout (FIG. 16 (e)) during the fifth light emission does not contribute to image formation. Therefore, this is substantially the same as that in the fifth light emission amount. Therefore, the same effect as in the case of the light emission shown in FIG.

FIG. 17 is a time chart in the case where charge reading is performed in the middle of the third, fourth, and fifth times of flash emission. In this case, the charge generated in the light receiving unit after the electronic shutter operation at the time of the third and fourth light emission is transferred to the overflow drain (OF
D). For this reason, a control pulse is applied to the overflow control gate (OFCG), and when this pulse is at a high level, the level of the OFCG is lowered and the charge is discarded to the OFD.

FIG. 18 is a time chart in the case where the electric charges up to the middle of the third, fourth and fifth times of the strobe light emission are discarded. In this case, the OFCG is set to a high level immediately before the third, fourth, and fifth strobe light emission, and is set to a low level during light emission. As a result, the charge during the OFCG high level period is discarded by the OFD, and the charge during the OFCG low level period is accumulated and read. Therefore, the effective value of the light emission amount is adjusted by adjusting the low level period of the OFCG. In the above description, the case where the light emission amount of each time is determined in advance has been described. It is also possible. For example, an operation similar to that of an auto strobe (a strobe that receives and integrates reflected light from a subject and stops emitting light when the integrated value reaches a constant value) can be performed.

In other words, instead of controlling each light emission with the light emission amount,
A control method based on the photometric integrated value of the reflected light from the subject can be considered. For example, in the case of the strobe light emission 4 in FIG. 2 (g), the ratio of the light emission amount of each time is controlled to 16: 4: 1, but the first time is a certain value V ₀ , and the second, third, and fourth times are V ₀ / 4,5 th is to stop the emission when it reaches V _0/16. In this case, control as shown in FIGS. 15 and 17 is possible. Further, as a modified example, it is also possible to store the first light emission amount only for the first light measurement, and to control the light emission amount so as to have a fixed ratio with the stored value after the second light measurement.

It is also conceivable that the first light emission always emits a fixed amount of light, the light is measured at that time, and the amount of second and subsequent light emission is controlled according to the result. In the case of an auto-strobe-like method, the response of the photometric circuit must be fast,
In the case of this method, it may be slow. As an example, if the photometry result is a standard value, the ratio of the light emission amount of each time is 16: 4: 1, if the photometry result is a small value, the ratio of the light emission amount of each time is 16: 8: 2,
If the photometry result is a large value, the ratio of the light emission amount of each time is 16: 2:
0.5. The characteristics at this time are shown in FIG. In the figure, the horizontal axis represents the reflectance of a subject at a specific distance, and the vertical axis represents the signal charge. And the light emission amount ratio 16: 8: 4:
The characteristics at 2: 1: 0.5 are ,,,,, respectively
When the three light emissions are 16: 4: 1, the characteristic is A, and when the three light emissions are 16: 8: 2, the characteristic is B, and the three light emissions are 16: 2:
The characteristic at 0.5 is C. Here, in the case of C, the signal does not saturate up to a subject having a reflectance of 200%. This reflectivity 2
00% of the subject is the distance Corresponds to a subject with a reflectance of 100%. Photometry is performed in the first light emission, and when the result is a small value, it means that the subject is dark, that is, there are not many subjects with high reflectance, and it is not necessary to increase the knee characteristic. Therefore,
In this case, the characteristic of B is good, and the second and subsequent light emission is controlled. If the photometric result of the first light emission is a large value, the control is performed in the opposite manner so that the characteristic of C can be applied to a high reflectance and an object at a short distance. Here, the control is performed in three stages. However, if the ratio of the light emission amount of each time is continuously changed according to the photometric value, the accuracy of the exposure control can be increased. The same applies to the method of controlling on the electronic still camera side (electronic shutter operation, light emission start / stop control).

Alternatively, preliminary light emission is performed in advance, and the light emission amount can be changed with reference to the photometry result at that time. Since the preliminary light emission is performed before the field of photographing, it is possible to select the optimum light emission amount from the first light emission. However, because of the preliminary light emission, it is necessary to increase the capacity of the capacitor C _1.

In the above description, the strobe light is emitted a plurality of times when the CCD is read out a plurality of times in one field period. However, the strobe light of the present invention is applicable to other cases. For example, the strobe of the present invention can also be used in a CCD as proposed in "Knee Characteristic Control of CCD Image Sensor" on pages 43 to 44 of the 1978 Television Society Conference of Japan. Figure 20 shows the CCD of this proposal.
FIG. 4 is an explanatory diagram showing a relationship between a charge accumulation characteristic and an X contact signal. That is, the maximum accumulated charge amount that can be stored in the light receiving unit is increased during light reception (V ₁ → V ₂ , V ₂ → V ₃ ). Therefore, the strobe light is emitted each time the maximum accumulated charge amount is changed.

FIG. 21 is an explanatory diagram showing the charge storage characteristics of a "CCD drive circuit" proposed by the present applicant in Japanese Patent Application No. 62-87393, together with an X contact signal for controlling a strobe of the present invention. is there. In this proposal, the maximum accumulated charge amount is fixed, and a constant charge is discarded during light reception to obtain knee characteristics. Also in this case, good results can be obtained by causing the strobe of the present invention to emit light a plurality of times.

In the above description, the electronic still camera and the strobe are described as being separated from each other. However, an electronic still camera having a built-in strobe may be used. When the electronic still camera has a built-in strobe, control becomes easy.

(Effects of the Invention) As described in detail above, in the electronic still camera of the present invention, the strobe light is emitted a plurality of times and the charge is read out a plurality of times within one frame shooting time to control the light emission amount or the electronic shutter. To adjust the amount of received light. Therefore, the output of the CCD does not saturate even in a high luminance range, and the dynamic range is widened. Therefore, even if there is a difference in the reflectance and the distance, it is possible to realize an electronic still camera in which the obtained image is not distorted in white or black.

Also, in the electronic still camera strobe of the present invention, 1
In addition to firing the flash several times during the frame shooting time,
At least one light emission was different from the others. For this reason, the output of the CCD is not saturated on the electronic still camera side, and the dynamic range is widened. Accordingly, it is possible to realize an electronic still camera strobe in which an image obtained by the electronic still camera does not become white or blackened even if there is a difference in the reflectance and the distance of the subject.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a schematic configuration of an electronic still camera, FIG. 2 is a time chart showing waveforms during operation of the apparatus of the present invention, FIG. 3 is an explanatory diagram showing a schematic configuration of a CCD, and FIG. 5 and 5 are explanatory diagrams showing the potential of the CCD, FIGS. 6 and 7 are characteristic diagrams showing the output characteristics of the CCD, FIGS. 8 and 9 are circuit diagrams showing the circuit configuration of the strobe, and FIG. Is a circuit diagram showing a circuit example of a strobe controller, FIG. 11 is a time chart at the time of operation of the controller, FIG. 12 is a circuit diagram showing another example of a strobe circuit configuration, and FIG. 13 is a state of strobe control. FIG. 14 is a circuit diagram showing another example of the controller circuit, FIGS. 15 to 18 are time charts showing the control states of the strobe and the CCD, and FIG. 19 is a charge accumulation according to the present invention. Characteristic diagrams showing an example of characteristics, FIG. 20 and FIG. 21 show light reception of a CCD. Is an explanatory view showing the relationship between sex and X contact signal. 1 ... CCD 2 ... Light receiving unit 3 ... Vertical transfer unit 4 ... Horizontal transfer unit 10 ... Strobe, 10a ... Boost circuit 10b ... Controller, 11 ... Lens system 12 ... Amplifier, 13 ... … Process circuit 14… Recording circuit 15… Video floppy 16… Photometry circuit 17 CPU 18 CCD drive circuit

Claims (5)

(57) [Claims] An electronic still camera having a solid-state image pickup device, which is used together with a strobe which emits light in synchronization with an external timing signal, wherein a plurality of timing signals are provided within one frame of photographing time during strobe photographing. A timing signal supply unit to be provided to the strobe; and a light reception amount adjustment unit that adjusts a light reception amount by performing an electronic shutter operation of the solid-state imaging device during at least one light emission of each light emission of the strobe. An electronic still camera, characterized in that: 2. An electronic still camera for photographing a still image, which is used together with a strobe whose start and stop of light emission are controlled by an external light emission start signal and a light emission stop signal. A light emission start signal and a light emission stop signal applying means for applying a plurality of sets of a light emission start signal and a light emission stop signal to the strobe during a photographing time; and at least one of the plurality of light emission start signals and a light emission stop signal emits light. An electronic still camera, comprising: time interval control means for making a time interval from a start signal to a light emission stop signal different from a time interval of another set. 3. A strobe for use with an electronic still camera having a solid-state image sensor, wherein a plurality of sets of a light emission start signal and a light emission stop signal given from the electronic still camera within a single frame shooting time during flash shooting. Wherein at least one set includes light emission start and stop means for performing light emission start and light emission stop based on a signal whose time interval between the light emission start signal and the light emission stop signal is different from that of the other sets. Strobe for electronic still cameras. 4. An electronic still camera used in conjunction with a strobe which emits light a plurality of times within one frame of photographing time, wherein at least one of the plurality of light emissions is different from the other light emission amounts. An electronic still camera, comprising: a light emission start signal generating means for generating a light emission start signal for causing the strobe to emit light a plurality of times. 5. A strobe for use with an electronic still camera, wherein the strobe emits light a plurality of times within one frame of photographing time in synchronization with a light emission timing signal from the electronic still camera. A light emitting means for emitting light at least once with a light emission amount different from that of the other times, a strobe for an electronic still camera.